Andrew Miller/For The Star-LedgerU.S. Sen. Robert Menendez, pictured in this May photo, paid just over $40,000 in state and federal taxes last year on $172,000 in taxable income, according to returns released by his campaign today.

TRENTON — U.S. Sen. Robert Menendez paid just over $40,000 in state and federal taxes last year on $172,000 in taxable income, according to returns released by his campaign today.

"We have a very straightforward income story," Paul Brubaker, a spokesman for Menendez, said. "We’ve got one salary, one secondary source of income."

In all, Menendez, a Democrat, earned $189,282 last year in pre-taxable income: $174,000 from his Senate salary and $15,282 from a rental home he co-owns in Union City. The taxable income is slightly lower because about $15,000 in pre-tax income went to a deferred IRA.

Mendendez, who relinquished his House seat in 2006 after his appointment to the Senate, released the last five years of tax returns. They show his taxable income gradually increased from $150,622 in 2007 to $171,874 last year, mostly based on increasing revenue from his rental property and increases in his Senate salary.

The senator’s federal tax rate last year was 21.4 percent, while his state tax rate was 5.2 percent.

The controversy surrounding the refusal of Mitt Romney, the presumptive Republican presidential nominee, to disclose more than two years of tax returns has stoked more interest in New Jersey candidates’ filings this year.

A week ago, Menendez’s challenger — state Sen. Joseph Kyrillos (R-Monmouth) — released three years of tax returns that showed he and his wife earned a combined annual income of at least $365,000 since 2008. Menendez, who is divorced, filed as a single head of household.

Menendez’s federal tax rate was about 21 percent, while Kyrillos’s was 37 percent. In comparison, Romney’s 2010 tax filing — the only one he has released — show he paid about 15 percent rate.

Menendez bought the Union City house for $47,500 in 1977 and has paid $44,706 in property taxes from 2007 to 2011.

Until 2010, he wrote off about $3,000 a year in losses from a previous stock sale.

The Menendez campaign said the senator’s "what you see is what you get" income is one of the lowest in the Senate, while Kyrillos — who is also a real estate broker and financial advisor — is required to do more than just disclose his tax returns. Unlike state senators, U.S. Senators are only allowed to earn up to $26,955 in outside salaries.

"Until we actually know who his clients are, how he actually derives this income — which does make us curious given how well he’s done in this challenging economic time we’re in — then he has not achieved that level of disclosure," Brubaker said.

The Kyrillos campaign challenged Menendez’s portrayal of himself as middle-class by highlighting expenses from his campaign finance reports in 2006 and 2012, including almost $100,000 on airfare and $27,000 in luxury hotel bills.

"Bob Menendez must be living in an alternate universe to believe that flying around on private jets and sipping champagne poolside at the Biltmore Hotel makes him a middle-class guy," Chapin Fay, the Kyrillos campaign manager, said.